By Pat McGivern
Thanksgiving, Christmas, and Easter Cacti are collectively called “Holiday Cacti,” named for the season in which they bloom. The first two are members of the Genus Schlumbergera, and will be the topic of this article.
Thanksgiving and Christmas Cactus are possibly the second most common plants (after poinsettia) enjoyed in North American households in December, but they had their origins in the tropics. They are from the plant family Cactaceae, or cactus, and the Genus is now known as Schlumbergera, but older works may refer to the prior name of Zygocactus.
These are succulent perennials which lack spines and are native to the South American tropics of Brazil, high in the Organ Mountains north of Rio de Janeiro. Like many tropical cacti, these holiday favorites are epiphytes, which means they live on other plants, using the other plant as substrate, or a place to live. (As opposed to a parasitic plant, which uses its host for nutrients).
The true “Christmas Cactus” is considered to be Schlumbergera x buckleyi, a hybrid between S. truncata and S. russelliana produced in the late 1840’s by William Buckley in England. This true Christmas Cactus has flat stem segments (cladodes) which are arcing, and the stem segment edges are scalloped. The flowers are pendent (hang downward) and are symmetrical, with petals evenly surrounding and no bend in the flower. While this plant is very popular and long lived, it is not the usual plant seen in stores for December holiday sale, as it blooms a bit late for December holiday marketing. They have been kept as holiday houseplants since the 1800’s, and have been known to live for 60 years or more, thus may be passed from one generation to the next. The flower colors are traditionally red, but also range to magenta and magenta with some white.
The plants most often sold as “Christmas Cactus” are actually Schlumbergera truncata cultivars, known as Thanksgiving Cactus. They bloom about a full month
or more before true Christmas Cactus, timely for holiday sales, but blooms may not last until December 25. The stem segments are more erect and spreading, and have
soft points at each end. The flowers of the Thanksgiving Cactus are asymmetrical with the bottom petals bent back, and the flower bends upward at the ovary, so that
the flower appears to bloom more horizontally outward. (Through my research for this article, I realized that my old plant in the photos is not a true Christmas Cactus,
but has the upright stems, pointed leaf segments, and bent flowers of a Thanksgiving cactus. It typically is in full bloom early November and again in March). Flower colors have been developed to range from almost pure white to a deep reddish violet.
Both of these types of tropical or jungle cacti appreciate moist soil with good aeration such as a peat based potting medium, bright indirect light, and cooler temperatures to set their flowers. The flowers are “thermo-photoperiodic,” meaning both cool temperatures and days and nights of fairly equivalent length trigger the budding. The plants can be easily propagated by taking a leaf segment, and planting it a quarter of its length deep in slightly sandy soil and keeping moist. They do not need a lot of fertilizer, feeding only two to four times per year prior to the end of October is recommended. They also reportedly bloom better when slightly potbound. These easy to care for plants can bring a wealth of indoor bloom just when we Iowans may need it most!